Selective voice frequency relay



p 1933- P. F. BECHBERGER ET AL ,131,424

SELECTIVE VOICE FREQUENCY RELAY Filed May a, 1954 2 Sheets-Sheet l wuswlidz :2

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P. F. BECHBERGER .ET AL SELECTIVE VOICE FREQUENCY RELAY Filed May 8, 1934 2 Sheets-Sheet 2 J? Eflechberyer U. A5. Thompson Freaan'ckjYolbamz attorney Patented Sept. 7, I 1 938 2,13 1

UNITED STATES PATENT OFFICE 2,131,424 SELECTIVE VOICE FREQUENCY RELAY Paul F. Bechberger, Bergenfield, N. J., Charles S. Thompson, Brooklyn, N. Y., and Frederick Holborn, Cedar Grove, N. J., assignors to The Western Union Telegraph Company, New York, N. Y., a corporation of New York Application May 8, 1934, Serial No. 724,540 7 Claims. (Cl. 175-320) This invention relates to alternating current rents IA and In flowing in the respective windings electro-magnetic devices, such as relays, which of the relay, may be built up to several times are selective to a particular frequency band and the value that could ordinarily be obtained. T are especially adapted for multi-channel carrier 'make this clear, we shall now refer to the princurrent telegraph systems, although their use ciples underlying our relay construction.

is not confined thereto. Referring to Fig. 1, let the following relations It is known that electro-magnets, relays and in the two inductively coupled resonant circuits similar devices, having only one magnetic circuit hold among the circuit constants: will not operate smoothly from an alternating 1 current source because the alternating flux bel l 2 =3 (1) 10 comes zero twice in each cycle. To overcome 0 this difilculty such devices have been made with RIZWLIK and Rzzw'lzK (2) I two magnetic circuits energized by currents supwhere plied at the same frequency but difiering in phase so that the magnetic torque applied to the (3) l5 armature will never become zero. It is desirable to obtain the two currents from the same source :21 times the resonant frequency. (4) and to obtain the phase difference by some phase K=the coefficient of coupling between shifting device. This has been accomplished in the two inductances L1 and L2. (5)

various ways, the shaded pole alternating cur M=the mutu l inductance between the 20 rerIitt relafyt beigg a cbtimmon appl ca two inductances L1 and L2, (6)

is o n e 1r more readiely g 223 2X; g g fi ggg Substituting forthe loose coupled transformer quencies than to other frequencies. The object f n L2 Its eqmva'lent transformer and 35 of our invention is to provide a relay of this chartlplymg 1/ C2 and R2 by acter in which the energizing windings will em- L body the inductance of the frequency discrimi- I;

nating circuit and to obtain both desirable characteristics, viz;frequency selection and smooth we have a clrcmt as m Operation over the responsive band Here the relations are-as follows:

In explaining the principles underlying our 1 invention and the manner of applying the same 7 (7) to relays, we shall refer to the accompanying drawings, in which (8) Figures 1 to 3, and 8 to 14 are diagrams ex- L2=(L1+L2)K (9) 35 planatory of the underlying principles; 7

Figures 4 and 5 are plotted curves showing NOW, if We refer b h leakage inducthe current and phase frequencycharacteristics tiinces (L1) 0f the equivalent transformer of of the coupled resonant circuits of relays em- 2 to the left side makmg a dissymmemcal 0 bodying invention and Operating under equivalent transformer of only two inductances,

certain stated conditions and changing the circuit constants to suit, we

Figures 8 to 14 are diagrams illustrating varihave the f w ous modified arrangements of the elements in The circuit relatlons now become the resonant circuits of the relay. R L K 10 46' Figures 6, 7 and 15 are schematic diagrams of 1+1) relays constructed in accordance with this in-' (11) vention.

In constructing an alternating current relaya, (12) responsive to and operating smoothly over a z (13) hand of frequencies, we provide the relay with 50 two windings which are arranged as elements of m n a practlcal va f K and freresonant circuits. By properly tuning and couqllency fo= and d t n ng how the curpling these two circuits we obtain the desired r n IA and B and th ir ph se i ference vary characteristics above mentioned. with frequency, we have the curves shown in 66 By proper use of resonant circuits the cur- Fig. 4-. It will be observed that this circuit has marked phase shifting and frequency discriminating properties.

Let us now take another example, namely, a band pass filter. Starting with a constant K type of band pass filter as shown in Fig. 2, f1 and f2 being the lower and upper frequency limits respectively, the circuit relations are as follows:-

Replacing the symmetrical equivalent transformer composed of two Li's and L2 in Fig. 2 by a dissymmetrical equivalent transformer of two inductances, we have a circuit as in Fig. 3.

Now the circuit relations are- Choosing practical values of f1=950 and f2 -1050 cycles and plotting the currents and their phase difference against frequency, we have fig. 5. This circuit is also seen to be satisfaccry.

The example shown in Fig. 3 is but one of many satisfactory circuits and is merely representative of resonant circuits and band pass filters. Diagrams of some other circuits which may be used are given in Figs. 8 to 14., inclusive.

In all of the various modifications, the series and shunt impedances of the selective network constitute the two energizing windings of the relay, as shown in Fig. 15. In the cases illustrated,

each winding is associated with a condenser.

It is sometimes desirable to design the two magnetic circuits with part of their paths in common, as shown in Fig. 6, thereby giving the desired coupling between the two frequency discriminating circuits.

In a multi-channel carrier telegraph system, relays of this type operating over the same band Width. and from the same value of impedance, would have the same value of Li. However, L2 will be different for each channel frequency. If now both windings on relays for all the channels are made to have the same inductance value, and the two circuits in each case are connected by a transformer as illustrated in Fig. 7, having a turn ratio of then the relays are interchangeable in the several channels insofar as the windings, magnetic circuits and moving parts are concerned. The interchangeable relay apparatus is embraced within the dotted line rectangles R in Fig. '7. In relays receiving a constant band width and employing the type of circuit exemplified by Figs. 3 and 13, the'turn ratio of the associated transformers is approximately directly proportional to the frequency to be received. In cases such as Figs. 8 and 10 a similar but inverse proportion is involved.

We have illustrated a number of circuit arrangements embodying our invention but it will be evident to engineers that other modifications can be made within the scope of our invention and within the purview of the appended claims.

We claim: 1. A relay adapted to be operated by current of a definite band of frequencies, comprising a network selective to said band of frequencies and having series and shunt branches, each branch including an inductive element and a condenser, said relay having energizing windings constituting respectively the inductive elements of the series and shunt branches of said network.

2. In a relay device as set forth in claim 1, meansfor increasing the flow of current in the relay windings by making the elements of each branch of the network resonant at approximately the frequency to be received.

3. An electromagnetic device responsive to a definite band of frequencies, comprising energizing windings arranged in series and shunt relation, condensers connected in circuit with each of said windings, said windings and condensers jointly constituting a network selective to said band of frequencies and excluding frequencies outside of said band.

4. An electromagnetic device responsive to a definite band of frequencies, comprising energizing windings arranged relation, condensers connected in circuit with each 'of said windings to form circuits resonant at approximately the desired frequency, said resonant circuits jointly constituting a network selective to said band of frequencies and excluding frequencies outside of said band.

5. An electromagnetic device responsive to a definite band of frequencies, comprising two magnetic circuits having a common path form 7 ing a portion of each circuit, energizing windings for said circuits and condensers connected .in circuit with each of 'said windings to form resonant circuits at a given frequency, said windings and condensers jointly constituting a network selective to said band of frequencies and excluding frequencies outside of said band, said common magnetic portion forming a coupling between said two circuits.

6. An electromagnetic device responsive to a definite range of frequencies comprising energizing windings, condensers connected to said windings, said windings and condensers jointly constituting a network selective to said range of frequencies.

'7. An alternating current relay having a plurality of flux producing elements, auxiliary impedance elements connected to said first named elements and causing the relay to respond to an exclusive range of frequencies.

PAUL F. BECHBERGER. CHARLES S. THOMPSON. FREDERICK HOLBORN.

in series and shunt 

